Year	Percent
1990	52.85
1991	52.52
1992	52.2
1993	51.87
1994	51.55
1995	51.22
1996	50.89
1997	50.57
1998	56
1999	55.64
2000	55.28
2001	54.96
2002	54.64
2003	54.33
2004	54.01
2005	53.69
2006	53.38
2007	53.06
2008	52.74
2009	52.43
2010	52.11
2011	51.79
2012	51.47
2013	51.16
2014	50.84
2015	50.52